Commit 2f4df001 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Steven Rostedt (VMware)

tracing: Add -mcount-nop option support

-mcount-nop gcc option generates the calls to the profiling functions
as nops which allows to avoid patching mcount jump with NOP instructions
initially.

-mcount-nop gcc option will be activated if platform selects
HAVE_NOP_MCOUNT and gcc actually supports it.
In addition to that CC_USING_NOP_MCOUNT is defined and could be used by
architectures to adapt ftrace patching behavior.

Link: http://lkml.kernel.org/r/patch-3.thread-aa7b8d.git-e02ed2dc082b.your-ad-here.call-01533557518-ext-9465@work.hoursSigned-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 07d04081
......@@ -749,6 +749,12 @@ ifdef CONFIG_FTRACE_MCOUNT_RECORD
CC_FLAGS_FTRACE += -mrecord-mcount
export CC_USING_RECORD_MCOUNT := 1
endif
ifdef CONFIG_HAVE_NOP_MCOUNT
ifeq ($(call cc-option-yn, -mnop-mcount),y)
CC_FLAGS_FTRACE += -mnop-mcount
CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
endif
endif
endif
ifdef CONFIG_HAVE_FENTRY
ifeq ($(call cc-option-yn, -mfentry),y)
......
......@@ -47,6 +47,11 @@ config HAVE_FENTRY
help
Arch supports the gcc options -pg with -mfentry
config HAVE_NOP_MCOUNT
bool
help
Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
config HAVE_C_RECORDMCOUNT
bool
help
......
......@@ -2950,12 +2950,14 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
p = &pg->records[i];
p->flags = rec_flags;
#ifndef CC_USING_NOP_MCOUNT
/*
* Do the initial record conversion from mcount jump
* to the NOP instructions.
*/
if (!ftrace_code_disable(mod, p))
break;
#endif
update_cnt++;
}
......
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